The Streptococci make up a medically important genera of microbes known to cause several types of disease in humans, including, for example, otitis media, conjunctivitis, pneumonia, bacteremia, meningitis, sinusitis, pleural empyema and endocarditis, and most particularly meningitis, such as for example infection of cerebrospinal fluid. Since its isolation more than 100 years ago, Streptococcus pneumoniae has been one of the more intensively studied microbes. For example, much of our early understanding that DNA is, in fact, the genetic material was predicated on the work of Griffith and of Avery, Macleod and McCarty using this microbe. Despite the vast amount of research with S. pneumoniae, many questions concerning the virulence of this microbe remain. It is particularly preferred to employ Streptococcal genes and gene products as targets for the development of antibiotics.
Transcription of DNA is often arrested at sites in DNA that trap a fraction of elongating RNA polymerase molecules that pass through, resulting in locked ternary complexes that cannot propagate or dissociate their RNA product. Transcript cleavage factors cleave the RNA in such complexes at the 3'-end, allowing RNA polymerase to back up and re-attempt to read through the potential trap (Borukhov et al. 1993. Cell 72:459-466). In addition to assuring efficient transcript elongation, transcript cleavage factors increase the fidelity of transcription since misincorporated bases at the 3'-end of the nascent RNA also lead to arrested complexes (Erie et al. Science 262:867-8730. Two transcript cleavage factors, greA and greB, have been identified in E. coli (Borukhov et al. 1993. Cell 30 72:459-466). greA-dependent transcript cleavage usually results in the removal of di- and trinucleotides from the 3'- of the stalled RNA. greB-dependent cleavage yields larger oligonucleotides, up to a length of nine nucleotides. Both proteins bind RNA polymerase. Neither the greA or greB proteins possess intrinsic nuclease activity rather they stimulate a nuclease activity inherent in RNA polymerase (Orlova et al. 1995. Proc. Natl. Acad. Sci., USA 92:4596-4600). The greA and greB proteins are homologous, sharing 38% sequence identity and 59% sequence similarity. The eukaryotic transcript elongation protein SII is similar to the greA and greB proteins in that it stimulates RNA cleavage from the 3'-end of RNA in a stalled complex but does not share significantly sequence homology with the greA and greB proteins (Borukhov et al. 1993. Cell 72:459-466).
greA and greB proteins and their homologues, such as the novel polypeptides and polynucleotides of the invention, are important for screening for and discovery of antimicrobial compounds, particularly to fill the unmet mdeical need of developing new classes of such antimicrobial compounds.
Clearly, there is a need for factors, such as greA/greB homologue of the invention, that may be used to screen compounds for antibiotic and antimicrobial activity and which may also be used to determine their roles in pathogenesis of infection, dysfunction and disease. There is a need, therefore, for identification and characterization of such factors which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptide of the present invention has sequence homology to a known prokaryotic transcript cleavage factor protein.